如何通过模型关系从三个相关表中获取数据？

Question

我有三个这样的表：

费用：-

1. expense_id
2. user_id

用户：-

1. user_id
2. employee_id

员工：-

1. employee_id
2. 名字
3. 姓氏

我想从expense.user_id = user.user_id 的员工表中获取first_name 和 last_name，我尝试了类似下面的方法，但我没有得到正确的数据。

费用模式：-

 public function users(){

    return $this->hasOne(User::class,'user_id','user_id');
}

用户模型：-

public function employee(){
    return $this->hasOne(Employee::class,'employee_id','user_id');
}

和员工模型：-

public function users()
{
    return $this->belongsTo(User::class,'employee_id');
}

我打电话是这样看的：-

<td>{{$expense->users->employee->first_name ." " . $expense->users->employee->last_name }}</td>

它显示数据，但不是预期的数据。

我的错误在哪里，应该怎么做？ 请帮忙！ 谢谢！

Answer 1

我建议你用这种方式重新设计你的数据库和关系：

Expense:-

id
user_id

User:-

id

Employee:-

id
user_id
first_name
last_name

对于BelongsTo 和HasOne 关系，请使用单名词：

class Expense extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

class User extends Model
{
    public function employee()
    {
        return $this->hasOne(Employee::class);
    }
}

class Employee extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }

    public function getFullNameAttribute()
    {
        return $this->first_name . ' ' . $this->last_name;
    }
}

最后，您可以像这样访问员工的全名：

$expense->user->employee->full_name;

Answer 2

class Expense extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

class User extends Model
{
    public function employee()
    {
        return $this->belongsTo(Employee::class);
    }
}

class Employee extends Model
{
    public function user()
    {
        return $this->hasOne(User::class);
    }

    public function getFullNameAttribute()
    {
        return $this->first_name . ' ' . $this->last_name;
    }
}

然后访问客户属性：

<td>{{$expense->user->employee->full_name}}</td>

Answer 3

我相信你在滥用雄辩的关系。

One To One Relationship.

One To Many Relationship

一对多关系用于定义一个关系 单个模型是一个或多个子模型的父模型。

试试这个吧。

use App\Models\Employee;
use App\Models\Expense;

// User model.
class User extends Authenticatable
{
    use HasFactory, Notifiable;

    protected $primaryKey = 'user_id';

    protected $table = 'users';

    public function employee()
    {
        return $this->hasOne(Employee::class, "employee_id", "employee_id");
    }

    public function expenses()
    {
        return $this->hasMany(Expense::class, "user_id", "user_id");
    }
    
}

// Expense model
class Expense extends Model
{
    use HasFactory;

    protected $primaryKey = 'expense_id';

    public function user()
    {
        return $this->belongsTo(User::class, "user_id", "user_id");
    }
}

// Employee model.
class Employee extends Model
{
    use HasFactory;

    protected $primaryKey = 'employee_id';

    public function user()
    {
        return $this->belongsTo(User::class, "employee_id", "employee_id");
    }
}

// 'create_users_table' migration.
class CreateUsersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->id('user_id');
            $table->unsignedBigInteger("employee_id");
            $table->timestamps();

            $table->foreign("employee_id")
                ->references("employee_id")
                ->on("employees")
                ->onDelete("cascade");
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('users');
    }
}

// 'create_expenses_table' migration.
class CreateExpensesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('expenses', function (Blueprint $table) {
            $table->id('expense_id');
            $table->unsignedBigInteger("user_id");
            $table->timestamps();

            $table->foreign("user_id")
                ->references("user_id")
                ->on("users")
                ->onDelete("cascade");

        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('expenses');
    }
}

// 'create_employees_table' migration.
class CreateEmployeesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('employees', function (Blueprint $table) {
            $table->id("employee_id");
            $table->string("first_name");
            $table->string("last_name");
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('employees');
    }
}

// Sample query 1.
App\Models\Expense::find(1)
    ->with(
        ["user" => function($query)
        {
            $query->with("employee");
        }])
    ->first();

// Sample output 1.
/*
=> App\Models\Expense {#4172
     expense_id: 1,
     user_id: 1,
     created_at: null,
     updated_at: null,
     user: App\Models\User {#4322
       user_id: 1,
       employee_id: 1,
       created_at: null,
       updated_at: null,
       employee: App\Models\Employee {#4330
         employee_id: 1,
         first_name: "john",
         last_name: "doe",
         created_at: null,
         updated_at: null,
       },
     },
   }

*/

// Sample query 2.
App\Models\Expense::with(
    ["user" => function($query)
    {$query->with("employee");
    }])->get();

// Sample output 2.
/*
=> Illuminate\Database\Eloquent\Collection {#4318
     all: [
       App\Models\Expense {#4320
         expense_id: 1,
         user_id: 1,
         created_at: null,
         updated_at: null,
         user: App\Models\User {#3382
           user_id: 1,
           employee_id: 1,
           created_at: null,
           updated_at: null,
           employee: App\Models\Employee {#4335
             employee_id: 1,
             first_name: "john",
             last_name: "doe",
             created_at: null,
             updated_at: null,
           },
         },
       },
       App\Models\Expense {#4323
         expense_id: 2,
         user_id: 1,
         created_at: null,
         updated_at: null,
         user: App\Models\User {#3382},
       },
     ],
   }
*/